Tying a user to a phone number does nothing but invade the privacy of most users, and slightly increase the costs for those who value their privacy.
Source: at https://smsprivacy.org/ I run an online service offering completely anonymous phone numbers for ~£3/mo. And note that you only need 1 month in order to get the account validated. Most places check the phone number once at account creation time and then never again.
Source: at https://smsprivacy.org/ I run an online service offering completely anonymous phone numbers for ~£3/mo. And note that you only need 1 month in order to get the account validated. Most places check the phone number once at account creation time and then never again.